Process for metal plating of substrates

ABSTRACT

Substrates, particularly plastics, are plated with metals by pretreatment of the substrate with phosphorus sesquisulfide in an organic solvent to deposit phosphorus sesquisulfide at the surface, followed by contacting the treated surface with a metal salt or complex thereof, to form a metal-phosphorus-sulfur compound and then with a solution of an alkali metal hydroxide or carbonate or ammonium hydroxide or a nonoxidizing mineral acid. The resulting treated surface is either conductive or is capable of catalyzing the reduction of a metal salt to produce a conductive surface. Such conductive surfaces are readily electroplated by conventional techniques.

United States Patent Quinn et al.

{54] PROCESS FOR METAL PLATING OF SUBSTRATES [72] Inventors: Edward J. Quinn, Tonawanda, N.Y.; John K; MacKay, Niagara Falls, Ontario,

[21] Appl. No: 47,887

[52] US. Cl .204/30, 117/47 A, 117/47 R, 117/71 R, 117/160 R, 106/1 [51 Int. Cl. ..C23b 5/60, B44d 1/092, C23c 3/02 [58] FieldofSearch ..117/47 A, 47 R, 160R,71 R; 204/30; 106/1 [56] References Cited UNITED STATES PATENTS 3,438,805 4/1969 Potrafke ..117/47 A [4 Feb. 115, 1972 Primary ExaminerAlfred L. Leavitt Assistant Examiner-Janyce A. Bell Attorney-Peter F. Casella, Donald C. Studley, Richard P. Mueller and James F. Mudd [57] ABSTRACT Substrates, particularly plastics, are plated with metals by pretreatment of the substrate with phosphorus sesquisulfide in an organic solvent to deposit phosphorus sesquisulfide at the surface, followed by contacting the treated surface with a metal salt or complex thereof, to fonn a metal-phosphorussulfur compound and then with a solution of an alkali metal hydroxide or carbonate or ammonium hydroxide or a nonoxidizing mineral acid. The resulting treated surface is either conductive or is capable of catalyzing the reduction of a metal salt to produce a conductive surface. Such conductive surfaces are readily electroplated by conventional techniques.

11 Claims, No Drawings PROCESS FOR METAL PLATING OF SUBSTRATES BACKGROUND OF THE INVENTION There is a rapidly increasing demand for metal plated articles, for example, in the production of low-cost plastic articles that have a simulated metal appearance. Such articles are in demand in such industries as automotive, home appliance, radio and television and for use in decorative containers and the like. Heretofore, the metal plating of plastics and the like has required many process steps, and generally such processes have been applicable to only one or a few related substrates. A new process for the metal plating of substrates is described in copending application Ser. No. 855,037, filed Sept. 3, 1969, now abandoned. It has now been discovered that the process can be improved to provide metal plated articles having improved thermal resistance and a more uniform degree of adhesion of the metal to the substrate.

It is an object of this invention to provide an improved process for the metal plating of plastics. Another object of the invention is to provide an improved process that is applicable to the plating of many different substrates. A further object of the invention is to provide articles having an adherent metal coating that is resistant to peeling, temperature cycling and corrosion. Such coatings are electrically conductive whereby static charges may be readily dissipated from the surfaces. The metal coatings further serve to protect the articles from abrasion, scratching and marring, reduce their porosity and improve their thermal conductivity. The process of this invention can be used for unidirectional mirrors and the like; water and liquid collecting devices and the like; protective coatings on houses, cars, boats, power line poles, street lights and the like; and in thermal control of clothing, houses and the like; and the like.

SUMMARY OF THE INVENTION This invention provides a process which comprises forming a metal-phosphorus-sulfur compound at the surface of a substrate to render the surface susceptible to conventional electroless plating and/or electrolytic plating. More particularly, this invention provides a process which comprises subjecting a substrate to phosphorus sesquisulfide so as to deposit phosphorus sesquisulfide at the surface and thereafter contacting the thus-treated surface with a solution of a metal salt or complex thereof to form a metal-phosphorus-sulfur compound and then with a solution of an alkali metal hydroxide or carbonate or ammonium hydroxide or a nonoxidizing mineral acid. In one aspect of the invention, the treated surface is subjected to electroless metal plating to deposit an electroless conductive coating on the surface. Thereafter, the article is electroplated so as to deposit an adherent metal coating of the desired thickness on the electroless conductive coating.

Also in accordance with the invention, there is provided an article having a metal-phosphorus-sulfur compound adherently formed at the surface of the substrate.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The process of this invention is applicable to substrates, such as plastics and to other substantially nonmetallic substrates. Suitable substrates include, but are not limited to, cellulosic and ceramic materials such as cloth, paper, wood, cork, cardboard, clay, porcelain, leather, porous glass, asbestos, cement, and the like.

Typical plastics to which the process of this invention is applicable include the homopolymers and copolymers of ethylenically unsaturated aliphatic, alicyclic and aromatic hydrocarbons such as polyethylene, polypropylene, polybutene, ethylenepropylene copolymers; copolymers of ethylene or propylene with other olefins, polybutadiene; polymers of butadiene, polyisoprene, both natural and synthetic, polystyrene and polymers of pentene, hexene, heptene, octene, 2-methyl-propene, 4-methyl-hexene-l, bicyclo (2.2.1)- 2-heptene, pentadiene, hexadiene, 2,3-dimethylbutadiene- 1,3,4-vinylcyclohexene, cyclopentadiene, methylstyrene, and

the like. Other polymers useful in the invention include polyidene, indenecoumarone resins; polymers of acrylate esters and polymers of methacrylate esters, acrylate and methacrylate resins such as ethyl acrylate, n-butyl methacrylate, isobutyl methacrylate, ethyl methacrylate and methyl methacrylate; alkyd resins; cellulose derivatives such as cellulose acetate, cellulose acetate butyrate, cellulose nitrate, ethyl cellulose, hydroxyethyl cellulose, methyl cellulose and sodium carboxymethyl cellulose; epoxy resins; furan resins (furfuryl alcohol or furfural ketone); hydrocarbon resins from petroleum; isobutylene resins (polyisobutylene); isocyanate resins (polyurethanes); melamine resins such as melamine-formaldehyde and melamine-urea-formaldehyde; oleo-resins; phenolic resins such as phenol-formaldehyde, phenolicelastomer, phenolic-epoxy, phenolic-polyamide, and phenolic-vinyl acetals; polyamide polymers, such as polyamides, polyamide-epoxy and particularly long chain synthetic polymeric amides containing recurring carbonamide groups as an integral part of the main polymer chain; polyester resins such as unsaturated polyesters of dibasic acids and dihyroxy compounds, and polyester elastomer and resorcinol resins such as resorcinol-formaldehyde, resorcinol-furfural, resorcinol-phenol-formaldehyde, resorcinol-polyamide and resorcinol-urea; rubbers such as natural rubber, synthetic polyisoprene, reclaimed rubber, chlorinated rubber, polybutadiene, cyclized rubber, butadiene-acrylonitrile rubber, butadiene-styrene rubber, and butyl rubber; neoprene rubber (polychloroprene); polysulfides (Thiokol); terpene resins; urea resins; vinyl resins such as polymers of vinyl acetal, vinyl acetate or vinyl alcohol-acetate copolymer, vinyl alcohol, vinyl chloride, vinyl butryal, vinyl chloride-acetate copolymer, vinyl pyrrolidone and vinylidene chloride copolymer; polyformaldehyde; polyphenylene oxide; polymers of diallyl phthalates and phthalates; polycarbonates of phosgene or thiophosgene and dihydroxy compounds such as bisphenols, thermoplastic polymers of bisphenols and epichlorohydrin (tradenamed Phenoxy polymers); graft copolymers and polymers of unsaturated hydrocarbons and an unsaturated monomer, such as graft copolymers of polybutadiene, styrene, and acrylonitrile, commonly called ABS resins, ABS-polyvinyl chloride polymers, recently introduced under the tradename of Cycovin; and acrylic polyvinyl chloride polymers, known by the tradename of Kydex 100.

The polymers of the invention can be used in the unfilled condition, or with fillers such as glass fiber, glass powder, glass beads, asbestos, talc and other mineral fillers, wood flour and other vegetable fillers, carbon in its various forms dyes, pigments, waxes and the like.

The substrates of the invention can be in various physical forms, such as shaped articles, for example, moldings, sheets, rods, and the like; fibers, films and fabrics, and the like.

In the first step of the preferred process of the invention, the substrate is treated with phosphorus sesquisulfide or dissolved in a solvent. Suitable solvents or diluents for the phosphorus sesquisulfide are solvents that dissolve the phosphorus sesquisulfide and which preferably swell the surface of a plastic without detrimentally affecting the surface of the plastic, Such solvents include the halogenated hydrocarbons and halocarbons such as chloroform, methyl chloroform, phenyl chloroform, dichloroethylene, trichloroethylene, perchloroethylene, trichloroethane, dichloropropane, ethyl dibromide, ethyl chlorobromide, propylene dibromide, monochlorobenzene, monochlorotoluene and the like; aromatic hydrocarbons such as benzene, toluene, xylene, ethyl benzene, naphthalene and the like; ketones such as acetone, methyl ethyl ketone, and the like; acetic acid; acetic acid trichloroethylene mixtures; carbon disulfide; and the like.

When a solution of phosphorus sesquisulfide is employed in the process, the solution concentration is generally in the range from about 0.0001 weight percent of phosphorus sesquisulfide based on the weight of the solution up to a saturated solution, and preferably from about 0.5 to about 2.5 percent. Prior to contacting the substrate with the phosphorus sesquisulfide, liquid or solution, the surface of the substrate should be clean. When a solution is used, the solvent generally serves to clean the surface. A solvent wash may be desirable when liquid phosphorus sesquisulfide is employed. The phosphorus sesquisulfide treatment is generally conducted at a temperature below the softening point of the substrate, and below the boiling point of the solvent. Generally, the temperature is in the range of about to 135 C., but preferably in the range of about to 75 C. The contact time varies depending on the nature of the substrate, the solvent and temperature, but is generally in the range of about 1 second to 1 hour or more, preferably in the range of about 1 to minutes.

As a result of the first treatment step, the phosphorus sesquisulfide is deposited at the surface of the substrate. By this is meant that the phosphorus sesquisulfide can be located on the surface, embedded in the surface and embedded beneath the surface of the substrate. The location of the phosphorus sesquisulfide is somewhat dependent on the action of the solvent on the surface if one is used.

Following the first treatment step, the substrate can be rinsed with a solvent, and then can be dried by merely exposing the substrate to the atmosphere or to inert atmospheres such as nitrogen, carbon dioxide, and the like, or by drying the surface with radiant heaters or in a conventional oven. Drying 1 times can vary considerably, for example, from one second to minutes or more, preferably 5 seconds to 10 minutes. The rinsing and drying steps are optional.

In the second treatment step of the process ofthe invention, the phosphorus sesquisulfide treated substrate is contacted with a solution of a metal salt or a complex of a metal salt, which is capable of reacting with the phosphorus to form a metal-phosphorus-sulfur compound. The term metalphosphorus-sulfur compound used herein, means the metalphosphorus-sulfur coating which is formed at the surface of the substrate. Without being limited to theory, the metalphosphorus-sulfur compound may be an ionic compound or a solution (alloy). The metals generally employed are those of Groups I8, I18, IVB, VB, VIB, V118, and VIII of the Periodic Table. The preferred metals are copper, silver, gold, chromium, vanadium, tantalum, cadmium, tungsten, molybdenum, and the like.

The metal salts that are used in the invention can contain a wide variety of anions. Suitable anions include the anions of mineral acids such as sulfate, chloride, bromide, iodide, fluoride, nitrate, phosphate, chlorate, perchlorate, borate, carbonate, cyanide, and the like. Also useful are the anions of organic acids such as formate, acetate, citrate, butyrate, vale-rate, caproate, stearate, oleate, palmitate dimethylglyoxime, and the like. Generally, the anions of organic acids contain l to 18 carbon atoms.

Some useful metal salts include copper sulfate, copper chloride, silver nitrate, nickel chloride and nickel sulfate.

The metal salts can be complexed with a complexing agent that produces a solution having the basic pI-I 7). Particularly useful are the ammonical complexes of the metal salts, in which one to six ammonia molecules are complexed with the foregoing metal salts. Typical examples include NiSO '6NH Ni(C I-l 00) '6Nl-l CuSO,,-6NH CuCl '6NI-l AgNO -6NH NiSO,-3NH CuSO -4NH NiCl-6NH Ni(NO -4NH and the like. Other useful complexing agents include quinoline, amines and pyridine. Useful complexes include compounds of the formula MX Q wherein M is the metal ion, X is chlorine or bromine and Q is quinoline. Typical examples include: CoCl Q CoBr Q NiCl Q NiBr Q CuCl Q CuBr Q, and ZnCl Q Useful amine complexes include the mono(ethylenediamine). bis-(ethylenediamine)-, tris(ethylenediamine)-, bis(l,2-propane diamine)-, and bis- (l,3-propanediamine)- complexes of salts such as copper sulfate. Typical pyridine complexes include NiCl (py) and CuCl(py) where py is pyridine.

The foregoing metal salts and their complexes are used in ionic media, preferably in aqueous solutions. However nonaqueous media can be employed such as alcohols, for example, methyl alcohol, ethyl alcohol, butyl alcohol, heptyl alcohol, decyl alcohol, and the like, Mixtures of alcohol and water can be used. Also useful are ionic mixtures of alcohol with other miscible solvents of the types disclosed hereinbefore. The solution concentration is generally in the range from about 0.1 weight percent metal salt or complex based on the total weight of the solution up to a saturated solution, preferably from about 1 to about 10 weight percent metal salt or complex.

The step of contacting the phosphorus sesquisulfide treated substrate with the solution of metal salt is generally conducted at a temperature below the softening point of the substrate, and below the boiling point of the solvent, if one is used. Generally, the temperature is in the range of about 30 to 1 10 C., preferably from about 50 to C. The time of contact can vary considerably, depending on the nature of the substrate, the characteristics of the metal salts employed and the contact temperature. However, the time of contact is generally in the range of about 0.1 to 30 minutes, preferably about 5 to 10 minutes.

In the third treatment step of the process of this invention, the substrate having the adherent metal-phosphorus-sulfur compound thereon is contacted with an aqueous solution of an alkali metal (Group IA) hydroxide, alkali metal carbonate, ammonium hydroxide or a nonoxidizing mineral acid. Typical solutes include lithium hydroxide, sodium hydroxide, potassium hydroxide, lithium carbonate, sodium carbonate, potassium carbonate, and the like alkali metal hydroxides and carbonates; hydrochloric acid, sulfuric acid and phosphoric acid. The solution concentration is generally in the range from about 0.4 weight percent solute based on the total weight of the solution up to a saturated solution, preferably from about 0.8 to about 2 weight percent solute. Generally, the contact temperature is in the range of about 30 to 1 10 C., preferably from about 50 to 100 C. The time of contacting can vary considerably, but is usually in the range of about 0.1 to 30 minutes, preferably, about 5 to 10 minutes. It has been particularly surprising to find that this treatment step results in improved thermal resistance of the metal plated article and a more uniform adhesion between the metal and the substrate because it has been observed that the contacting ofthe treated substrate with the solution results in the removal of an appreciable proportion of the metal-phosphorus-sulfur compound formed in the previous treatment step.

Depending on the conditions employed in the treatment steps, the duration of the treatments, and the nature of the substrate treated, the resulting treated surface may be either (1) conductive, such that the surface can be readily electroplated by conventional techniques, or (2) nonconductive. In the latter instance, the treated surface contains active or catalytic sites that render the surface susceptible to further treatment by electroless plating process that produce a conductive coating on the plastic surface. Such a conductive coating is then capable of being plated by conventional electrolytic processes.

In a typical electroless plating or chemical plating process, a catalytic surface is contacted with a solution of metal salt under conditions in which the metallic ion of the metal salt is reduced to the metallic stage and deposited on the catalytic surface. The use of this process with the products of this invention relies upon the catalytic metal sites deposited on the surface as a result of the treatment with the solution of metal salt or complex of this invention. A suitable chemical treating bath for the deposition ofa nickel coating on the catalytic surface produced in accordance with the process of the invention can comprise, for example, a solution of nickel salt in an aqueous hypophosphite solution. Suitable hypophosphites include the alkali metal hypophosphite such as sodium hypophosphite and potassium hypophosphite, and the alkaline earth metal hypophosphites such as calcium hypophosphite and barium hypophosphite. Other suitable metal salts for use in the chemical treating bath include the metal salts described hereinbefore with respect to the metal salt treatment of the phosphorus-treated substrate of the invention. Other reducing 2.5 moles per liter) maintained at 60 C. After drying, the media include formaldehyde, hydroquinone and hydrazine. black plastic surface had a resistance of 10,000 ohms per cen- Other agents, such as buffering agents, complexing agents, timeter.

and other additives are included in the chemical plating solui tions or baths. 5 EXAMPLE 16 The treated substrate of the invention that are conductive jcan be electroplated by the processes known in the art. The i polyPl-opylene plaque was "l m a 50 bath P- i article is used as the cathode. The metal desired to be plated is i tammg mchloroethylene for 15 minutes and then treated as m igenemuy diss 0! ve d in an aqueous plating bath although other Example 15. The resistance of the resulting treated plastic surimedia can be employed. Generally, a soluble metal anode of face was 9 ohms i" cenimieterfl'rhe Sawple was ythe metal to be plated can be employed. In some instances, 1 troplated to give a 0.3 mil semibright nickel str ke and 1.7-mil ihowever, a carbon anode or other inert anode is used. Suitable i 2 5;2 :2122 g SEES? i f g The adhesion was deter .metals, solutions and condition for electroplating are p P i described in Metal Finishing Guidebook Directory for 1967, 5

published by Metals and Plastics Publications, Inc. Westwood, EXAMPLE 17 I An epoxy resin-glass fiber resin laminate was immersed for The fPnowmg amp e Serve to Illustrate the mvenno but 5 minutes in a 1.3 percent solution of phosphorus sesquisulare not intended to limit it. Unless specified otherwise, all temfide in methylene chloride at room temperature, dried in air peratures are m degrees cent grade and parts are understood 2 f 10 Seconds and then immersed for 10 minutes in an to be expressed in parts by weight.

moniacal solution ofnickel sulfate at 60C. The resistance of EXAMPLE! I the black preplate was 5,000 ohms per centimeter. The

' l t th 1 ltd. A sample of polypropylene sheet was immersed for 2. g l fi ervas ,effafiereectropae minutes in a solution containing 2 percent by weight phosphorus sesquisulfide in a mixture of 700 milliliters ofj EXAMPLES 18-26 :trichloroethylene, 700 milliliters of perchloroethylene and 14. I A 2 percent l i f phosphorus i lfid was mill li of ethanol at The Sample was thereafter i prepared in the following specified solvents. Thereafter, sammersed f0! 10 minutes in a solution Of copper pyrophosphate ples of polypropylene, ABS, phenolic resin, epoxy resin, and at 60 C. The copper pyrophosphate solution was prepared by 5 l i l hl id were i d i h phosphorus adding the following ingredients o Wa er f l y dilution l 5 sesquisulfide solution for 3 minutes at 50 C. and transferred t 6 lite s of solution and filtering: 223 grams copper Oxide, to an ammoniacal nickel sulfate bath at 65 C. for minutes. 2,660 grams tetrapotassium pyrophosphate trihydra e. 2 Each of the experiments were repeated replacing the nickel grams oxalic acid, 40 grams of 30 volume percent aqueous with a bath containing an ammoniacal solution of 5 percent of m and grams of 70 p r y l m aqueous copper sulfate. In every instance, a metal-phosphorus-sulfur nitric acid. A red conductive copper-phosphorus-sulfur coatcompound was fo m d, ing was produced on the surface of the polypropylene. f I Thereafter, layers of nickel and chrome were adherently I bound to the polypropylene by electrodeposition as follows: i I The articles was plated in a bath of semibright nickel Trichlommethane (Harshaw Co.) employed a current density of 50 amperes per g: fif ifg fgzzrl square foot, followed by plating in a bath of bright nickelg 2| Benzene (Harshaw Co.) at 50 amperes per square foot current density 5 -22 Toluene and then plating in a chrome bath (Udylite Corp.) at 150 am- :2 3:22;?

peres per square footcurrerit density. H I" 25 mmemynormamide 2 l4 26 Dimethylsulfoxide Following the procedure of Example 1, a metal-phosphorus- Q EXAMPLE 27 sulfur coating was obtained on the following specified plastics by employing a 2 percent solution of phosphorus sesquisulfide Following the procedure of Example 18, the following metal in trichloroethylene and perchloroethylene followed by subsalts were employed in the metal salt bath to obtain a metaljection of the thus-treated plastic to the specified metal salt= phosphorus-sulfur compound: nickel chloride, nickel nitrate, baths. Table lspecifies the plastic, metal salt bath and the apnickel acetate, nickel formate, nickel citrate, silver nitrate, pearance of the resulting metal-phosphorus-sulfur coating. iron chloride and colbalt chloride.

TABLE I Example Plastic Metal Salt Bath Appearance 2 Polypropylene Copper pyrophosphate in water. Red coating. 3. ..do. Ammoniacal nickel sulfate Black coating. 4. .do- Copper sulfate Coppery coating. 5 Ammoniacal nickel sulfate.... Black coating. 6. .do. Gray coating. 7. do. Black coating. 8. o. Black and yellow coating. 9 -.do- Slate colored coating. 10 Copper pyrophosphate in wate Red coating. 11 o o Transparent amber coating. 2.-. P01yvinylaceta e-polyvinylehlorlde. do.... Dull olive gray coating, 13 Filled polypropylene--- ..do.... Brown and Yellow coating. 4 ABS ...d0 Shiny olive gray coating.

EXAMPLE [5 f EXAMPLE 28 A mol p lypropyl n p q was imm r for L Following the procedure of Example 18, the following subminutes in a 1 percent solution of phosphorus sesquisulfide in, strates were provided with an adherent meta] coating: novolac trichloroethylene at room temperature, rinsed with water and resin, cotton string, Teflon, cardboard, leather, rubber, immediately immersed for 10 minutes in an aqueous solution masonite, ceramics, wood, Lexan (polycarbonate), nylon,

containing nickel sulfate (0.063 mole per liter) and ammonia; "polyape t yl, e l :rylics fplexiglass and polystyrene.

An epoxy resin-glass fiber laminate was immersed for minutes at room temperature in a 1 percent solution of phosphorus sesquisulfide dissolved in a 2:1 (by volume) solvent mixture of trichloroethylene and methylene chloride. After being rinsed in a water bath, the laminate was immersed for 15 minutes in an aqueous solution, at 65 C., containing nickel sulfate (0.063 mole per liter) and ammonia (2.5 mole per liter). The sample was rinsed with water and then immersed in an aqueous electroless copper bath for minutes at room temperature. The electroless copper bath had the following composition.

CuNO,-3H,O g. per liter NaHCO 10 g. per liter Rochelle salt 30 g. per liter NaOH g. per liter Formaldehyde (37%) I00 ml. per liter After drying the sample was electroplated with 0.3 mil semibright nickel and 1.7 mil acid copper.

EXAMPLE 30 An epoxy resin-glass fiber laminate was treated as in Example 29 except that an electroless nickel bath instead of electroless copper was used. The electroless nickel bath had the following composition.

minutes, and then electroplated as described in Example 29.

EXAMPLE 31 Twenty-two discs of Eastman 4231 polypropylene were immersed in perchloroethylene for 2 minutes at 65 C. and then for 15 minutes in a one weight percent P.,S solution in perchloroethylene at about 325 C. Thereafter, the discs were immersed for 15 minutes in aqueous copper chloride-ethylene diamine at about 70 C. Fourteen of the discs were washed with 2 weight percent aqueous acetic acid for 1 minute and then with water for 1 minute at ambient temperatures. The other eight discs were washed with water for 1 minute at ambient temperature, immersed for 15 minutes in a 0.36 M sodium hydroxide solution at about 70 C. and then washed with water for 1 minute at ambient temperature. All samples wee thereafter placed in an oven for 30 minutes at about 82.5i2.5 C. Each sample was thereafter successively electroplated with 0.1 mil semibright nickel, 0.8 mil acid copper, 0.5 mil semibright nickel, 0.2 mil bright nickel and 0.01 mil chromium. Each metal plated disc was subjected to a three cycle thermal shock test. Each cycle consisted of placing the disc in a freezer at about 35 C. for one hour and transferring the disc immediately into boiling water for 30 minutes. Twentyfour of the 28 sides of the 14 discs that had not been metal plated according to the process of this invention exhibited a high degree of blistering. In contrast, no blistering was observed in the eight discs which had been treated with the sodium hydroxide.

The foregoing procedure was repeated except that after removal from the copper bath, the discs were washed with water only before being oven dried. A high degree of blistering was exhibited on substantially all sides tested.

EXAMPLE 32 Following the procedure of Example 31, similar results are obtained when the sodium hydroxide is replaced with potassium hydroxide, lithium hydroxide, sodium carbonate, lithium carbonate, potassium carbonate, sulfuric acid and phosphoric acid.

EXAMPLE 33 EXAMPLE 34 Example 33 was repeated except that the HCl was replaced with a 29% Nl-l Ol-l solution. The plated samples had an average adhesion ofabout 24.7 pounds per inch.

Various changes and modifications can be made in the process and products of this invention without departing from the spirit and scope of the invention. Various embodiments of the invention disclosed herein serve to further illustrate the invention but are not intended to limit it.

We claim:

1. A process which comprises subjecting a substrate to a solution phosphorus sesquisulfide to deposit phosphorus sesquisulfide at the surface of the substrate, subjecting the phosphorus sesquisulfide treated surface to a solution of a metal salt or complex thereof so as to form a metalphosphorus-sulfur compound wherein said metal is selected from Groups 18, H8, IVB, VB, VIB, VllB, and VIII of the Periodic Table, and thereafter subjecting the thus-treated substrate to an aqueous solution of a member of the group consisting of alkali metal hydroxides, alkali metal carbonates, ammonium hydroxide, sulfuric acid, hydrochloric acid and phosphoric acid.

2. The process wherein the treated substrate resulting from the process of claim 1 is electroplated to deposit an adherent metal coating on the treated substrate.

3. The process of claim 1 wherein the substrate is a plastic.

. The process of claim 3 wherein the solvent is a halogenated hydrocarbon.

5. The process of claim 4 wherein the metal of said metal salt is selected from the group consisting of nickel and copper.

6. The process according to claim 5 wherein said aqueous solution is a solution ofsodium hydroxide.

7. The process according to claim 5 wherein said aqueous solution is a solution of sulfuric acid.

8. The process according to claim 5 wherein said aqueous solution is a solution of hydrochloric acid.

9. The process of claim 1 wherein the substrate is polypropylene, the phosphorus sesquisulfide is employed as a solution of phosphorus sesquisulfide dissolved in perchloroethylene, the metal salt complex is a complex of copper and said aqueous solution is a solution of sodium hydroxide.

10. The process of claim 1 wherein said metal salt is employed as a solution of the ammonia complex thereof and the treated substrate resulting from said process is electroless metal plated to deposit an electroless conductive coating on the treated substrate.

11. A process wherein the substrate resulting from the process of claim 10 is electroplated to deposit an adherent metal coating on the electroless conductive coating. 

2. The process wherein the treated substrate resulting from the process of claim 1 is electroplated to deposit an adherent metal coating on the treated substrate.
 3. The process of claim 1 wherein the substrate is a plastic.
 4. The process of claim 3 wherein the solvent is a halogenated hydrocarbon.
 5. The process of claim 4 wherein the metal of said metal salt is selected from the group consisting of nickel and copper.
 6. The process according to claim 5 wherein said aqueous solution is a solution of sodium hydroxide.
 7. The process according to claim 5 wherein said aqueous solution is a solution of sulfuric acid.
 8. The process according to claim 5 wherein said aqueous solution is a solution of hydrochloric acid.
 9. The process of claim 1 wherein the substrate is polypropylene, the phosphorus sesquisulfide is employed as a solution of phosphorus sesquisulfide dissolved in perchloroethylene, the metal salt complex is a complex of copper and said aqueous solution is a solution of sodium hydroxide.
 10. The process of claim 1 wherein said metal salt is employed as a solution of the ammonia complex thereof and the treated substrate resulting from said process is electroless metal plated to deposit an electroless conductive coating on the tReated substrate.
 11. A process wherein the substrate resulting from the process of claim 10 is electroplated to deposit an adherent metal coating on the electroless conductive coating. 